Field of the Invention
The disclosed technology generally relates to magnetic memory devices, and more particularly to spin transfer torque magnetic random access memory (STT-MRAM) devices having a magnetic tunnel junction (MTJ) cell and methods of fabricating the STT-MRAM devices.
Description of the Related Technology
Magnetic random access memory (MRAM) is emerging as an alternative to conventional semiconductor memories such as SRAM, DRAM and/or flash memory. Compared to volatile memories such as SRAM and DRAM, MRAM can be advantageous because it can be designed to be non-volatile (e.g., data retention of >10 years). Compared to non-volatile memories such as flash memory used for storage application, MRAM can be advantageous because it can offer high endurance (e.g., greater than 106 cycles of memory access).
As compared to field-switchable MRAM devices that were studied in the earlier part of the last decade, spin transfer torque magnetic random access memory, also referred to as spin-torque transfer magnetic random access memory (STT-MRAMs), have gained popularity in part due to their potential to be scaled to very small sizes. It has been recognized that scalability of STT-MRAMs can be limited by thermal stability, as well as by writability. Two different geometries, one with an in-plane magnetization direction and another one with an out-of-plane (perpendicular) magnetization direction, have been proposed. It has been suggested that, while the former may be implemented at entry level, the latter may be more promising to be implemented as a more scalable geometry of the two different geometries of magnetic tunnel junction (MTJ) cells, especially from switching and thermal stability perspectives.
A STT-MRAM device typically includes an MTJ element which in turn includes a tunnel barrier layer sandwiched between a reference layer and a free layer. As there are a lot of scaling issues and device performance issues (for example thermal stability of the device) to tackle when going down to sub-1×nm technology, there is a further need for improved STT-MRAM device and methods for fabricating such a device.